Acid-resistant sulfur material and method for application of acid-resistant sulfur material

ABSTRACT

The present invention provides an acid-resistant sulfur material that has excellent strength, and is capable of exhibiting excellent corrosion resistance and excellently maintaining appearance even in a strongly acidic environment, a high concentration hydrogen sulfide environment, or a high concentration sulfur-oxidizing bacterial environment. The invention also provides a method of constructing such an acid-resistant sulfur material. The acid-resistant sulfur material contains a modified sulfur and an aggregate, the modified sulfur having been prepared by polymerizing sulfur with a sulfur modifier. The aggregate is an inorganic aggregate containing at least Si, and a weight ratio of Ca, Si, and Al in the aggregate in terms of oxides expressed as CaO/(SiO 2 +Al 2 O 3 ) is not higher than 0.2.

FIELD OF ART

The present invention relates to acid-resistant sulfur materials thatmay be used as materials for civil engineering or construction productsutilizing sulfur, and that have excellent acid resistance, and to amethod of constructing such sulfur materials.

BACKGROUND ART

In acid soil areas such as hot-spring areas, concrete materials, such asHume pipes, tend to be eroded by the action of sulfate or sulfite ionsin the acid soil. Concrete materials for sewerage are eroded in a shorttime in the areas where sulfuric acid is generated in sewage by theaction of organic substances and bacteria, and prematurely requirerepairing or renewal.

In such environments requiring acid resistance, plastic materials suchas polymers produced by mixing and molding polyvinyl chloride orunsaturated polyester with aggregates, are used for constructing sewerpipes and the like. However, plastic materials are expensive, hard to bemade into large products, and unusable in hot soils such as inhot-spring areas.

Antimicrobial concrete Hume pipes are in production, which inhibitpropagation of sewage bacteria on the pipe surface. However, such Humepipes are capable of inhibiting propagation of bacteria only on the pipesurface, and are not made of an acid resistant material, so that theseHume pipes tend to be eroded when brought into contact with acid.

Acid-resistant materials are disclosed, for example, in JP-2000-72523-A,which proposes sulfur concrete products produced by consolidating sulfurand mineral powders. These consolidated sulfur concrete products haveusually about one-third the strength of, and at most slightly poorerstrength than, concrete containing cement, and are not satisfactory instrength as civil engineering or construction stock materials. Stillless, these sulfur concrete products do not have sufficient acidresistance to survive the environment of not higher than pH 3.5.

JP-2001-253759-A discloses a sulfur composition containing sulfur andgranulated coal ash coated with cement for producing molded productshaving excellent strength and acid resistance. The cement and coal ashcontribute to maintenance of the strength of the produced moldedproducts initially after construction, and the sulfur gives some acidresistance. However, the crystal structure of sulfur changes with thelapse of time to cause shrinkage of the molded products, sometimesaccompanied by cracks. Poor acid resistance of cement allows acidcorrosion to proceed from the cracks to lower the strength of theproducts. Thus these products can hardly be used as actual civilengineering or construction stock materials for use in acid soils orsewage, which require certain acid resistance.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an acid-resistantsulfur material that may be used for producing civil engineering orconstruction products for use in acid soil areas or sewerage, that maybe made into molded products having the same or higher strength thanthat of conventional concrete products containing cement, and that iscapable of exhibiting superior corrosion resistance and excellentlymaintaining its appearance even in a strongly acidic environment, a highconcentration hydrogen sulfide environment, or a high concentrationsulfur-oxidizing bacterial environment.

It is another object of the present invention to provide a method ofconstructing an acid-resistant sulfur material wherein the sulfurmaterial is constructed in an environment of not higher than pH 3.5,with superior strength, corrosion resistance, and appearance beingmaintained.

According to the present invention, there is provided an acid-resistantsulfur material comprising a modified sulfur and an aggregate, saidmodified sulfur having been prepared by polymerizing sulfur with asulfur modifier,

-   -   wherein said aggregate is an inorganic aggregate comprising at        least Si, or at least Ca and Si, and    -   wherein a weight ratio of Ca, Si, and Al in the aggregate in        terms of oxides expressed as CaO/(SiO₂+Al₂O₃) is not higher than        0.2.

According to the present invention, there is also provided a method ofconstructing an acid-resistant sulfur material comprising the steps of:

-   -   producing a civil engineering or construction product with the        above-mentioned acid-resistant sulfur material, and    -   placing said product in an environment of not higher than pH        3.5.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a production system for producing amaterial containing a modified sulfur used in Example 3.

FIG. 2 shows photocopies of photographs showing the appearance ofspecimens prepared in Examples 1 to 3 and Comparative Examples 1 and 2after the test of resistance to an aqueous solution of acid (sulfuricacid).

FIG. 3 shows photocopies of photographs showing the appearance ofspecimens prepared in Examples 1 to 3 and Comparative Examples 1 and 2after the test of resistance to an aqueous solution of acid(hydrochloric acid).

FIG. 4 shows photocopies of photographs showing the appearance ofspecimens prepared in Examples 1 to 3 and Comparative Example 1 afterthe test of resistance to sulfur-oxidizing bacteria.

FIG. 5 shows photocopies of photographs showing the appearance ofspecimens prepared in Examples 1 to 3 and Comparative Example 1 afterthe evaluation of accelerated concrete corrosion.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will now be explained in detail.

The acid-resistant sulfur material according to the present inventioncontains a modified sulfur obtained by polymerizing sulfur with a sulfurmodifier, and a particular aggregate, and is substantially free ofcement.

The sulfur for preparing the modified sulfur is an ordinary, elementalsulfur, and may be natural sulfur or sulfur generated by desulfurizationof oil or natural gas.

The sulfur modifier for preparing the modified sulfur may be, forexample, dicyclopentadiene (DCPD), tetrahydroindene (THI), or one ormore compounds selected from the group consisting of olefin compoundssuch as cyclopentadiene, oligomers thereof (mixtures of dimers topentamers), dipentene, vinyl toluene, and dicyclopentene.

As used herein, “DCPD” means DCPD alone, or a mixture mainly composed ofcyclopentadiene and a dimer to pentamer thereof. The mixture has a DCPDcontent of not lower than 70 mass %, preferably not lower than 85 mass%. Thus most of the commercially available products referred to asdicyclopentadiene may be used.

As used herein, “THI” means THI alone, or a mixture of THI and amaterial mainly composed of one or more members selected from the groupconsisting of cyclopentadiene, polymers of cyclopentadiene, polymers ofbutanediene, and a dimer to pentamer of cyclopentadiene. The mixture hasa THI content of usually not lower than 50 mass %, preferably not lowerthan 65 mass %. Thus most of the commercially available productsreferred to as tetrahydroindene, and by-product oils discharged fromethylnorbornene production plants may be used as THI in the presentinvention.

The amount of the sulfur modifier used in preparation of the modifiedsulfur is preferably 0.01 to 30 parts by weight, more preferably 0.1 to20 parts by weight, based on 100 parts by weight of sulfur.

The modified sulfur may be prepared, for example, by mixing sulfur andthe sulfur modifier in molten states to polymerize the sulfur. Themixing in molten states may be carried out, for example, in an internalmixer, roll mill, drum mixer, pony mixer, ribbon mixer, homo mixer, orstatic mixer, with a line mixer such as a static mixer beingparticularly preferred. The line mixer allows production of homogeneousmodified sulfur, improves productivity of the modified sulfur, andprovides sufficient modification of sulfur even with a small amount ofthe sulfur modifier. Further, the line mixer inhibits evaporation lossof the sulfur modifier caused by heat from the molten sulfur, so thateven as small as 0.1 to 10 parts by weight of the sulfur modifier basedon 100 parts by weight of sulfur, gives the objective modified sulfur.

The amount of the sulfur modifier used in preparing the modified sulfuris one of the factors for improving properties of the acid-resistantsulfur material of the present invention, such as fire-resistance, watersealability, and resistance to sulfur-oxidizing bacteria. The moresulfur modifier is used, the more these properties are improved.However, at about 30 parts by weight of the sulfur modifier to 100 partsby weight of sulfur, the improvement in these properties by the modifiedsulfur reaches the maximum, and further increase in the amount will notresult in much change. On the other hand, less than 0.01 parts by weightof the sulfur modifier hardly gives sufficient strength to the resultingmolded product.

The modified sulfur may be prepared, for example, by mixing sulfur andthe sulfur modifier in molten states at 120 to 160° C. in a mixer suchas a line mixer, and retaining the mixture until its viscosity at 140°C. falls in the range of 0.05 to 3.0 Pa·s. The temperature in the linemixer for melting and mixing is preferably 130 to 155° C., morepreferably 140 to 155° C., for achieving effective modification ofsulfur.

The initial reaction between sulfur and the sulfur modifier occurred inthe line mixer is an exothermic reaction to generate a precursor ofmodified sulfur through the reaction between sulfur and the sulfurmodifier. Thus under the observation that no sudden temperature riseoccurs in the line mixer, sulfur and the sulfur modifier arecontinuously stirred in the line mixer to gradually increase thetemperature to 120 to 160° C.

In reacting sulfur and the sulfur modifier in the line mixer, aprecursor of modified sulfur is generated having a molecular weight of150 to 500 as measured by gel permeation chromatography (GPC), andusually 0.01 to 45 wt %, preferably 1 to 40 wt % of the precursor ofmodified sulfur is generated in the reaction system.

The molecular weight of the precursor may be measured by GPC using thesulfur mixed with the sulfur modifier dissolved in carbon disulfide ortoluene. For example, the molecular weight may be measured by GPC usinga sample solution containing 1 mass/vol % carbon disulfide at a flowrate of 1 ml/min at room temperature, with chloroform as an eluent and aUV detector at 254 nm, and determined against a calibration curveobtained from polystyrene standard.

The line mixer may be a static mixer. Generally, a static mixer hasbaffles arranged in a fluid flow passage such as a pipe, and mixesfluids by splitting flows of the fluids with the baffles to change theirstreamlines. The static mixer used in preparation of the modified sulfurhas preferably one or more, more preferably 4 to 32 twisted vaneelements arranged in the pipe.

The flow rate and the pressure in the line mixer may suitably be decideddepending on the diameter of the pipe or the amount of the product, andthe preferred flow rate is about 0.1 to 100 cm/sec. The treatment timein the line mixer is usually about 1 second to 30 minutes. After thereaction between sulfur and the sulfur modifier starts to generate theprecursor of modified sulfur, the sulfur modifier no longer evaporates,so that the line mixer may not be used after the commencement of thereaction. Further, the reaction product containing sulfur and theprecursor of modified sulfur discharged from the line mixer may beintroduced into and retained in a holding tube to polymerize theprecursor of modified sulfur and the molten sulfur for increasing themolecular weight of the product. The holding tube preferably has staticmixer elements therein.

The residence time in the holding tube may suitably be decided dependingon the diameter of the tube or the amount of the product, and maypreferably be for about 1 minutes to about 1 hour. The residence timemay also vary depending on the amount of the sulfur modifier or thetemperature for melting.

When to terminate the reaction for sulfur modification may be decidedtaking the viscosity of the melt into account. For example, the reactionmay preferably be terminated when the viscosity of the melt at 140° C.falls in the range of 0.05 to 3.0 Pa·s. In view of the strength of theresulting product molded from the modified sulfur and the workabilityduring its production process, it is comprehensively most preferred toterminate the reaction when the viscosity at 140° C. falls in the rangeof 0.05 to 2.0 Pa·s.

When the viscosity is less than 0.05 Pa·s, the strength of the civilengineering or construction products obtained from the modified sulfuris too low, and the modifying effect of the sulfur modifier is notsufficiently expressed. With the increase in the viscosity, themodification proceeds, and the strength of the resulting modified sulfuralso increases. However, with the viscosity exceeding 30 Pa·s, themodified sulfur is hard to be molded, and the workability issignificantly impaired, thus not being preferred.

The line mixer allows easy control of the molecular weight distributionof the resulting modified sulfur to fall within the range of usually 200to 3000, preferably 200 to 2500, and provides a narrower molecularweight distribution than a batch mixer, with the average molecularweight being maintained at a comparable level (350 to 550).

The modified sulfur in the acid-resistant sulfur material of the presentinvention is a sulfur polymerized and modified through the reaction ofsulfur and the sulfur modifier, and may contain pure sulfur. Bycombining this modified sulfur with the particular aggregate of thepresent invention, civil engineering or construction products ofexcellent acid resistance and strength capable of surviving theenvironment of not higher than pH 3.5 may be obtained, which environmentcannot be survived by conventional civil engineering or constructionproducts made of, for example, concrete containing cement.

The aggregate used in the acid-resistant sulfur material of the presentinvention contains at least Si, or at least Ca and Si, and optionallyAl. The aggregate is an inorganic aggregate wherein a weight ratio ofCa, Si, and Al in terms of oxides expressed as CaO/(SiO₂+Al₂O₃) is nothigher than 0.2, in other words, 0 to 0.2, and when the aggregatecontains at least Ca and Si, the weight ratio expressed asCaO/(SiO₂+Al₂O₃) is preferably 0.01 to 0.2, more preferably 0.1 to 0.2.Such inorganic aggregate may be one or more kinds of aggregates mainlycomposed of silica components, such as coal ash, silica sand, silica,quartz powders, quartz rocks, gravel, sand, clay minerals, and glasspowders. When the CaO/(SiO₂+Al₂O₃) weight ratio of the aggregate exceeds0.2, desired acid resistance cannot be achieved. Thus, blast furnaceslag, incinerated ash, and the like having a CaO/(SiO₂+Al₂O₃) weightratio exceeding 0.2 are substantially not usable in the acid-resistantsulfur material of the present invention. The weight ratio of Ca, Si,and Al in the aggregate is determined by calculating the Ca, Si, and Alcontents in terms of CaO, SiO₂, and Al₂O₃, respectively. The aggregatemay not contain Ca or Al, which are optional components.

The coal ash may be conventional coal ash discharged from various coalcombustion furnaces such as those for power generation or for heating,and may be, for example, fly ash, clinker ash, or bottom ash.

The inorganic aggregate preferably contains not less than 5 wt %,preferably 5 to 50 wt % of an aggregate having an average particle sizeof not larger than 100 μm, in order to further increase the mechanicalstrength of the various civil engineering or construction products madewith the acid-resistant sulfur material of the present invention.Examples of such aggregate include fly ash and silica sand, both ofwhich may be used in the present invention, with fly ash beingparticularly preferred. Here, the average particle size is determined bylaser diffraction.

The acid-resistant sulfur material of the present invention mayoptionally contain other aggregates free of Ca and/or Si, as long as theeffects of the present invention are not impaired.

In the acid-resistant sulfur material of the present invention, themixing ratio of the modified sulfur and the aggregate is usually 1 to5:9 to 5 by weight. It is most preferred that the modified sulfur is insuch an amount as to fill the gaps in the aggregate consolidated to themaximum density. At such a ratio, the maximum strength of the sulfurmaterial is achieved. When the amount of the modified sulfur is lessthan 10 wt %, or the amount of the aggregate is more than 90 wt %, thesurface of the inorganic material as the aggregate cannot be wetsufficiently and is left exposed, resulting in insufficient expressionof the strength and incapability of maintaining the water sealability.When the amount of the modified sulfur is more than 50 wt %, or theamount of the aggregate is less than 50 wt %, the properties of theresulting sulfur material are similar to those of the modified sulfuralone, and the strength may not be high enough.

The mixing ratio of the modified sulfur and the aggregate may also varydepending on the kind of aggregate or the kind of civil engineering orconstruction products to be produced. It is thus desirable to suitablyselect the mixing ratio from the above-mentioned range, taking thesefactors into account.

In addition to the above-mentioned modified sulfur and the particularaggregate, the acid-resistant sulfur material of the present inventionmay optionally contain a fiber filling in order to further improve thebending strength required depending on the kind of civil engineering orconstruction products to be produced. Specifically, by adding a fiberfilling to the acid-resistant sulfur material of the present inventionin preparing civil engineering or construction products such as panelsor tiles, the resulting products may be made thinner or lighter.

Examples of the fiber filling may include carbon fibers, glass fibers,steel fibers, amorphous fibers, vinylon fibers, polypropylene fibers,polyethylene fibers, aramid fibers, and mixtures of two or more ofthese.

A preferred diameter of the fiber filling is usually 5 μm to 1 mm, whichmay vary depending on its material. The fiber filling may either beshort or continuous fibers, and the length of the short fibers ispreferably 2 to 30 mm for allowing uniform dispersion. The continuousfibers may preferably be a lattice material having mesh that allowpassage of the aggregate, and such lattice material may have either awoven or non-woven fabric structure.

The content of the fiber filling may usually be 0.5 to 10 vol %,preferably 1 to 7 vol % of the acid-resistant sulfur material.

The acid-resistant sulfur material of the present invention may furthercontain fibrous particles and/or flake particles, in order to improvethe toughness of the civil engineering or construction products to beproduced.

Examples of the fibrous particles may include wollastonite, bauxite, andmullite, each having an average length of not longer than 1 mm. Examplesof the flake particles may include mica flakes, talc flakes, vermiculiteflakes, and alumina flakes, each having an average particle size of notlarger than 1 mm.

The content of the fibrous particles and/or flake particles is usuallynot higher than 35 wt %, preferably 10 to 25 wt % of the total amount ofthe acid-resistant sulfur material.

The acid-resistant sulfur material of the present invention may beprepared, for example, by mixing the modified sulfur in a molten state,the aggregate, and optionally other materials, and cooling. The modifiedsulfur may be melted upon mixing with the aggregate, or may be kept in amolten state in advance of mixing with the aggregate in a storagecontainer such as a storage tank capable of storage at 120 to 140° C.,and mixed in a molten state with the aggregate. By keeping the modifiedsulfur in such a storage container, and using a desired amount asrequired, continuous production may be effected, rather than batchproduction.

The modified sulfur in a molten state, the aggregate, and optionallyother materials may be mixed usually at 120 to 160° C., preferably at130 to 140° C., usually for 5 to 30 minutes, while the viscosity of themodified sulfur at 140° C. is maintained in the range of 0.05 to 3.0Pa·s. After the mixing, the resulting mixture is cooled down to nothigher than 120° C., to thereby providing a desired acid-resistantsulfur material.

The viscosity of the modified sulfur during the mixing in a molten stateshould be kept in a preferred optimum viscosity range that allows easyhandling, since the viscosity increases as the polymerization of sulfurproceeds with the lapse of time. The preferred viscosity range for themodified sulfur is 0.05 to 3.0 Pa·s at 140° C. If the viscosity is lessthan 0.05 Pa·s, the strength of the resulting sulfur material tends tobe too low. The higher the viscosity is, the higher the strength of theresulting material is. However, if the viscosity is higher than 3.0Pa·s, the stirring operation in the production process becomes hard, andthe workability is remarkably deteriorated, thus not being preferred.

Before the mixing operation, it is preferred to pre-heat the aggregateto about 120 to 155° C., and the mixer to 120 to 155° C., in order toavoid temperature drop in the mixing.

The duration of the mixing in a molten state is preferably as short aspossible as long as the properties of the resulting product permit, foravoiding too high a viscosity or curing of the mixture due to thepolymerization of sulfur and the sulfur modifier. However, if theduration of mixing is too short, the modified sulfur and the aggregateare not mixed sufficiently, so that the resulting material will not begiven a continuous phase and will have gaps and a rough surface. Withsufficient mixing, the resulting material will be given a perfectlycontinuous phase with smooth surface. Thus the duration of mixing mustbe decided suitably depending on the properties of the acid-resistantsulfur material to be obtained.

The mixer to be used in the mixing is not particularly limited as longas thorough mixing is provided, and may preferably be a solid-liquidmixer such as an internal mixer, roll mill, ball mill, drum mixer, screwextruder, pug mill, pony mixer, ribbon mixer, or kneader.

After the mixing in a molten state, the resulting mixture is cold moldedinto an acid-resistant sulfur material of the present invention inaccordance with a known method, depending on the kind of products to beproduced, such as civil engineering or construction products. The coldmolding may be carried out by pouring the mixture into a mold, cooling,and solidifying into a desired shape. For molding tubular products, suchas Hume pipes and manholes, centrifugal casting may be employed. Formolding box culverts, panels, tiles, and blocks, the mixture may bepoured into a mold and vibration molded. The molding may be performedunder suitable vibration or with irradiation with ultrasonic wave forconsolidation.

The acid-resistant sulfur materials of the present invention may beplaced in various locations. For making use of their excellentacid-resistance, the present acid-resistant sulfur materials arepreferably placed in accordance with the following construction methodof the present invention.

The method of constructing the acid-resistant sulfur material of thepresent invention includes the steps of producing a civil engineering orconstruction product with the above-mentioned acid-resistant sulfurmaterial, and placing the product in an environment of not higher thanpH 3.5.

Examples of the civil engineering or construction products may includeHume pipes, box culverts, manholes, tiles, blocks, panels, flooringmaterials, and wall materials, and the panels may also be used as repairpanels for sewerage. As road products, U-shaped gutters, side ditches,curb blocks, L-shaped blocks, plates, and interlocking blocks areincluded. As building products, building blocks, piles, Hume pipes, fishreefs, wave dissipating blocks, and breakwater blocks are included. Ascivil engineering materials, earth retaining walls, retaining walls,L-shaped retaining walls, and sheet piles are included.

The acid-resistant sulfur material does not have to be used all over thecivil engineering or construction products, but may be used only inparts which are brought into contact with acid for achieving the objectsof the present invention. For example, a Hume pipe may be lined on itsinner surface with the acid-resistant sulfur material, and have aconcrete outer wall. Similarly in other usage, such as in box culverts,manholes, tiles, blocks, panels, flooring materials, and wall materials,the acid-resistant sulfur material may be combined with concrete toprovide a double-layered structure, or even a triple-layered structurewith the acid-resistant sulfur materials arranged on both sides ofconcrete.

The environment in which the civil engineering or construction productsare to be placed may be any environment as long as the pH of theenvironment could be not higher than pH 3.5, and may include sewagetreatment facilities, wherein pH is of such value, and acidic hot-springfacilities, wherein pH could be 1.5 or lower.

Since the acid-resistant sulfur material according to the presentinvention contains the modified sulfur and the particular aggregate, thematerial exhibits excellent corrosion resistance, strength, durability,and capability of maintaining appearance, even in a strongly acidicenvironment, a high concentration hydrogen sulfide environment, or ahigh concentration sulfur-oxidizing bacterial environment. Thus thepresent sulfur material is particularly useful for producing civilengineering or construction products for use in acid soils and sewerage.Further, since the method of construction according to the presentinvention employs the above-mentioned acid-resistant sulfur material,Hume pipes, box culverts, manholes, tiles, blocks, panels, and the likestructures may be constructed with expected long-term durability, evenin the environment of not higher than pH 3.5.

EXAMPLES

The present invention will now be explained with reference to Examplesand Comparative Examples, but the present invention is not limited tothese. Each molded product prepared in Examples and Comparative Exampleswas measured and evaluated in accordance with the following methods.

Evaluation of Resistance to Aqueous Solution of Acid

Each specimen prepared in Examples and Comparative Examples was soakedat room temperature in a 10 wt % sulfuric acid aqueous solution or a 10wt % hydrochloric acid aqueous solution for six months, and taken out toevaluate the degree of degradation. As the indices of degradation,change of the appearance, weight change calculated from the weightmeasured after the moisture on the specimen surface was wiped off, andstrength loss calculated from the compressive strength measured, werecompared. The strength loss was determined by measuring the compressivestrength of each specimen after the test using TENSILON compressivestrength measuring equipment at the pressure of 30 tons, and comparingthe measured value with the referential compressive strength measured onthe seventh day after the preparation of the specimen measured in thesame manner.

The results of the test using the aqueous solution of sulfuric acid forsoaking are shown in Table 1, and the corresponding photographs showingthe appearance of the specimens (A) to (E) are shown in FIG. 2. Theresults of the test using the aqueous solution of hydrochloric acid forsoaking are shown in Table 2, and the corresponding photographs showingthe appearance of the specimens (A) to (E) are shown in FIG. 3.

Evaluation of Resistance to Sulfur-Oxidizing Bacteria

A specimen in the form of a 2 cm×2 cm×4 cm prism and 100 ml of a culturesolution (2.0 g of NH₄Cl, 4.0 g of KH₂PO₄, 0.3 g of MgCl₂.6H₂O, 0.3 g ofCaCl₂.2H₂O, 0.01 g of FeCl₂.4H₂O, and 1.0 liter of ion exchange water,adjusted to pH 3.0 with hydrochloric acid) were placed in a 500 mlbaffled (ribbed) flask, inoculated with a starter (sulfur-oxidizingbacteria, Thiobacillus thiooxidans IFO 12544) and subjected to bacterialculture with rolling and shaking (170 rpm) in a thermostatic chamber at28° C. Four months after the inoculation, the weight change and theappearance of each specimen prepared in Examples and ComparativeExamples were determined. When sulfur is consumed by thesulfur-oxidizing bacteria, sulfate ions are generated, and the weight ofa specimen decreases. The results are shown in Table 3, and photocopiesof the photographs showing the appearance of specimens (A) to (D) areshown in FIG. 4.

Evaluation of Accelerated Concrete Corrosion

Each specimen prepared in Examples and Comparative Examples except forComparative Example 2 was placed in a thermostatic chamber maintained atthe humidity of not lower than 95%, the temperature of 30° C., and thehydrogen sulfide concentration of 200 ppm by weight, for 12 months, andevaluated for corrosion. As the indices of degradation, change of theappearance, weight change calculated from the weight measured after themoisture on the specimen surface was wiped off, and strength losscalculated from the compressive strength measured, each of after thetwenty-month test, were compared. The strength loss was determined bymeasuring the compressive strength of each specimen after the test usingTENSILON compressive strength measuring equipment at the pressure of 30tons, and comparing the measured value with the referential compressivestrength measured on the seventh day after the preparation of thespecimen measured in the same manner. The results are shown in Table 4,and photocopies of the photographs showing the appearance of thespecimens (A) to (D) are shown in FIG. 5.

Example 1

950 g of solid sulfur was placed in a hermetically sealed internalmixer, heated at 120° C. to melt, and maintained at 130° C. Then 50 g ofdicyclopentadiene previously heated to about 50° C. to melt was addedslowly, and softly stirred for about 10 minutes. After the temperaturerise due to the initial reaction was confirmed to converge, the reactionmass was heated to 150° C. The reaction was started, and the viscositygradually rose. When the viscosity reached 0.1 Pa·s in about 1 hour, theheating was immediately terminated, and the resulting material waspoured into a suitable mold or a container, and cooled at roomtemperature, to thereby obtain modified sulfur (A).

Next, an aggregate pre-heated to 140° C. consisting of 100 g of coal ashhaving an average particle size of 50 μm and the CaO/(SiO₂+Al₂O₃) weightratio of 0.1 and 690 g of silica sand having an average particle size of250 μm and the CaO/(SiO₂+Al₂O₃) weight ratio of less than 0.1, and 210 gof a molten material prepared by re-heating the modified sulfur (A) intoa molten state were introduced substantially simultaneously into a mixermaintained at 140° C. The materials were kneaded for 10 minutes, andpoured into a columnar mold of 5 cm in diameter and 10 cm in height, andcooled to obtain specimen (A).

Example 2

Specimen (B) was prepared in the same way as in Example 1, except thatthe aggregate was replaced with an aggregate consisting of 780 g ofsilica sand having an average particle size of 250 μm and theCaO/(SiO₂+Al₂O₃) weight ratio of less than 0.1.

Example 3

Using system 10 for producing a material containing modified sulfur asshown FIG. 1, a material was prepared. The production system 10 includestanks 11 and 12, static mixer 13 consisting of stirring tube 13 b andholding tube 13 c both disposed in a heat reserving chamber 13 a,cooling tank 14, storage tank 15, and batch mixer 16.

Sulfur, which was melted in the tank 11 maintained at 140° C. andsupplied therefrom at the flow rate of 660 g/min by a fixed deliverypump, and dicyclopentadiene, which was melted in the tank 12 maintainedat 140° C. and supplied therefrom at the flow rate of 35 g/min, wereintroduced into the stirring tube 13 b (length 10 cm, inner diameter11.0 mm, with 17 elements) of the static mixer 13 maintained at 150° C.at the liquid linear velocity of 0.4 m/min, and the two materials werestirred in the stirring tube 13 b to continuously generate reactionprecursors. The mixture was passed through the holding tube 13 cmaintained at 150° C. over 5-minute residence time, and then through thecooling tank 14 of a static mixer type (length 18 cm, inner diameter11.0 mm, with 24 elements) maintained at 130° C. to immediately cool themixture to 130° C., to thereby prepare a molten modified sulfur having aviscosity of 1 Pa·s at 140° C., an average particle size of 450 measuredby GPC, and a molecular weight distribution of 200 to 2000. The moltenmaterial was temporarily stored in the storage tank 15 maintained at130° C. It was demonstrated that the production system 10 was capable ofproducing 42 kg/hr of the modified sulfur.

Next, 21 kg of the molten modified sulfur stored in the storage tank 15was introduced into the mixer 16 maintained at 140° C., andsimultaneously an aggregate pre-heated to 140° C. consisting of 69 kg ofsilica sand having an average particle size of 250 μm and theCaO/(SiO₂+Al₂O₃) weight ratio of less than 0.1 and 10 kg of coal ashhaving an average particle size of 50 μm and the CaO/(SiO₂+Al₂O₃) weightratio of 0.1 was also introduced into the mixer 16. The materials werekneaded for 10 minutes, poured into a columnar mold of 5 cm in diameterand 10 cm in height, and cooled to obtain specimen (C).

Comparative Example 1

12.44 kg of normal Portland cement (manufactured by HITACHI CEMENT CO.),31.42 kg of sand having particle sizes of not larger than 5 mm (fromKimitsu, Chiba, Japan), 34.41 kg of gravel having particle sizes of notlarger than 5 mm (from Otsuki, Yamanashi, Japan), and 5.72 kg of waterwere kneaded in a concrete mixer, and cast in a columnar mold of 5 cm indiameter and 10 cm in height. After the mixture was set, the product wasdemolded, and cured in water for 28 days, to thereby obtain specimen(D).

Comparative Example 2

Specimen (E) was prepared in the same way as in Example 1, except thatthe aggregate was replaced with an aggregate consisting of 780 g ofblast furnace slag having particle sizes of not larger than 10 mm, andthe CaO/(SiO₂+Al₂O₃) weight ratio of 0.9.

Example 4

Specimen (F) was prepared in the same way as in Example 1, except thatthe aggregate was replaced with an aggregate consisting of 780 g ofquartz powders having an average particle size of 250 μm and theCaO/(SiO₂+Al₂O₃) weight ratio of 0. TABLE 1 Example Example ExampleExample Comp. Ex. Comp. Ex. 1 2 3 4 1 2 Kind of Specimen SpecimenSpecimen Specimen Specimen Specimen Specimen (A) (B) (C) (F) (D) (E)Appearance No No No No Corroded Slightly change Change change changeCorroded, Swollen Weight 0 0 0 0 −62 +8 Change (%) Initial 59.8 51.762.9 51.7 35.2 65.8 Strength (MN/m²) Strength 1.2 3.9 0.9 3.9 100 13.2Loss (%)

TABLE 2 Example Example Example Example Comp. Ex. Comp. Ex. 1 2 3 4 1 2Kind of Specimen Specimen Specimen Specimen Specimen Specimen Specimen(A) (B) (C) (F) (D) (E) Appearance No No No No Corroded Slightly changeChange change change Corroded, Swollen Weight 0 0 0 0 −27 +2 Change (%)Initial 59.6 51.3 63.2 51.3 35.0 65.8 Strength (MN/m²) Strength 0.9 3.20.4 3.2 100 6.7 Loss (%)

From Tables 1 and 2 as well as FIGS. 2 and 3, it is understood that thespecimens (A) to (C) and (F) prepared in Examples 1 to 3 maintained theoriginal state prior to the test even after the soaking for 6 months,while the specimen (D) prepared using the normal concrete in ComparativeExample 1 was significantly corroded to loose its original shape. Thespecimen (E) prepared in Comparative Example 2 using the blast furnaceslag having the CaO/(SiO₂+Al₂O₃) weight ratio of 0.9 as the aggregatewas observed to be corroded on its surface in the presence of sulfuricacid. Thus it was understood that the specimens (A) to (C) and (F)prepared in Examples 1 to 4 underwent little change in appearance andweight, and small compression strength loss, and exhibited extremelyhigh resistance to an aqueous solution of acid. TABLE 3 Example ExampleExample Example Comp. Ex. 1 2 3 4 1 Kind of Specimen Specimen SpecimenSpecimen Specimen Specimen (A) (B) (C) (F) (D) Appearance No No No NoCorroded change Change change change Weight 0 0 0 0 −49 Change (%)

From Table 3 and FIG. 4, it is understood that the specimens (A) to (C)and (F) prepared in Examples 1 to 4 underwent little change inappearance and weight, and exhibited high resistance to thesulfur-oxidizing bacteria. Through the same evaluation, the specimen (D)prepared in Comparative Example 1 using the normal concrete wasconfirmed to be corroded significantly in the habitat of thesulfur-oxidizing bacteria. TABLE 4 Example Example Example Example Comp.Ex. 1 2 3 4 1 Kind of Specimen Specimen Specimen Specimen SpecimenSpecimen (A) (B) (C) (F) (D) Appearance No No No No Corroded changeChange change change Weight 0 0 0 0 −62 Change (%) Initial 59.9 51.663.7 51.6 35.4 Strength (MN/m²) Strength 0.3 1.1 0.1 1.1 100 Loss (%)

From Table 4 and FIG. 5, it is understood that the specimens (A) to (C)and (F) prepared in Examples 1 to 4 underwent little change inappearance and weight, and small compression strength loss during thetwelve-month evaluation, and exhibited extremely high corrosionresistance under the concrete-corroding environment such as in sewerageor wastewater treatment sites, compared to the specimen (D) prepared inComparative Example 1 using the normal concrete.

1. An acid-resistant sulfur material comprising a modified sulfur and anaggregate, said modified sulfur having been prepared by polymerizingsulfur with a sulfur modifier, wherein said aggregate is an inorganicaggregate comprising at least Si, and wherein a weight ratio of Ca, Si,and Al in the aggregate in terms of oxides expressed as CaO/(SiO₂+Al₂O₃)is not higher than 0.2.
 2. The acid-resistant sulfur material of claim1, wherein a ratio of said modified sulfur to said aggregate in thesulfur material is 1 to 5:5 to 9 by weight.
 3. The acid-resistant sulfurmaterial of claim 1, wherein said aggregate comprises one or moremembers selected from the group consisting of coal ash, silica sand,silica, quartz powders, gravel, sand, clay minerals, and glass powders.4. The acid-resistant sulfur material of claim 1, wherein said aggregatecomprises not less than 5 wt % of an aggregate having an averageparticle size of not larger than 100 μm.
 5. The acid-resistant sulfurmaterial of claim 1 further comprising one or more members selected fromthe group consisting of fiber filling, fibrous particles, flakeparticles, and mixtures thereof.
 6. A method of constructing anacid-resistant sulfur material, comprising the steps of: producing acivil engineering or construction product with an acid-resistant sulfurmaterial of claim 1, and placing said product in an environment of nothigher than pH 3.5.
 7. The method of claim 6, wherein said civilengineering or construction product is a Hume pipe, manhole, boxculvert, tile, block, or panel.